Eigenfunction expansion for a regular fourth order eigenvalue problem with eigenvalue parameter in the boundary conditions.
Eigenvalue approximation
Eigenvalue Inequalities for the Dirichlet Problem on Spheres and the Growth of Subharmonic Functions
Ein Äquikonvergenzsatz für eine Klasse von singulären Differentialoperatoren.
Ein Gegenbeispiel zur Stabilität des absolut stetigen Spektrums gewöhnlicher Differentialoperatoren.
Estimates on the eigenvalues for some nonlinear ordinary differential operators
Estimations asymptotiques des valeurs propres de l'équation de Hill polynomiale
Expansion of solutions of T'Hooft's equation. A study in the confluence of analytic boundary conditions.
Explicit solutions for non homogeneous Sturm-Liouville operators problems.
In this paper we study existence and sufficiency conditions for the solutions of Sturm-Liouville operator problems related to the operator differential equation X'' - QX = F(t). Explicit solutions of the problem in terms of a square root of the operator Q are given.
Explicit solutions for Sturm-Liouville operator problems (II).
It is proved that the resolution problem of a Sturm-Liouville operator problem for a second-order differential operator equation with constant coefficients is solved in terms of solutions of the corresponding algebraic operator equation. Existence and uniqueness conditions for the existence of nontrivial solutions of the problem and explicit expressions of them are given.